For a negative active material for a rechargeable lithium battery, a carbon-based material is generally used. The carbon-based material is classified into crystalline carbon and amorphous carbon, and the crystalline carbon includes natural graphite and artificial graphite. The natural graphite has recently been used as a negative active material due to its low cost, good voltage flatness, and large charge and discharge capacity.
Electrochemical characteristics of a negative active material for a rechargeable lithium battery are known to be affected by shapes of negative active material particles. Spherically shaped graphite has low anisotropy, and thus maintains uniformity of voltage and current distribution.
During charge and discharge of a rechargeable lithium battery, a graphite-based carbonaceous negative active material undergoes intercalation and deintercalation of lithium ions into graphite layers. High-rate charge and discharge characteristics depend on lithium ion diffusion speed into graphite particles. As the graphite particle size is reduced, high-rate charge and discharge characteristics may be improved, and thus small graphite particles as a negative active material have been required.